title: Methoxy-substituted isoTQEN family for enhanced fluorescence response toward zinc ion.
abstract: Previously, we have reported that 1- and 3-isoTQENs (N,N,N',N'-tetrakis(1- or 3-isoquinolylmethyl)ethylenediamines) exhibit a specific fluorescence enhancement toward zinc ion. In this study, three methoxy-substituted derivatives of 1-isoTQEN were synthesized and their fluorescent response toward zinc ion was studied. The substitution pattern of the methoxy group significantly changes the solubility of compounds in aqueous DMF, λ(max) in the absorption spectra, excitation/emission wavelengths and fluorescence intensity of zinc complexes. In the presence of zinc ion, 7-MeO-1-isoTQEN exhibits higher fluorescence intensity and longer excitation/emission wavelengths (λ(ex) = 342 nm, λ(em) = 526 nm) than 6-MeO-1-isoTQEN (λ(ex) = 303 nm, λ(em) = 469 nm) and 5,6,7-triMeO-1-isoTQEN (λ(ex) = 340 nm, λ(em) = 504 nm). The fluorescence intensity of a zinc complex of 7-MeO-1-isoTQEN (ϕ = 0.122) is four times higher than the parent 1-isoTQEN (ϕ = 0.034) under the same conditions. The crystal structure of 7-MeO-1-isoTQEN-Zn complex reveals that all six nitrogen atoms participate to the metal coordination with ideal octahedral geometry, affording significantly high metal binding affinity comparable with TPEN (N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine). 7-MeO-1-isoTQEN detects zinc ion concentration change in cells by fluorescence microscopic analysis.
authors.affiliation: KYOUSEI Science Center, Nara Women's University, Nara, 630-8506, Japan. mikata@cc.nara-wu.ac.jp
authors.forename: Yuji
authors.initials: Y
authors.lastname: Mikata
authors.forename: Azusa
authors.initials: A
authors.lastname: Yamashita
authors.forename: Keiko
authors.initials: K
authors.lastname: Kawata
authors.forename: Hideo
authors.initials: H
authors.lastname: Konno
authors.forename: Saori
authors.initials: S
authors.lastname: Itami
authors.forename: Keiko
authors.initials: K
authors.lastname: Yasuda
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tamotsu
mesh_terms: D000818:Animals; D018360:Crystallography, X-Ray; D005029:Ethylenediamines / Q000138:chemical synthesis / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D042541:Intracellular Space / Q000737:chemistry; D007546:Isoquinolines / Q000138:chemical synthesis / Q000737:chemistry*; D016716:PC12 Cells; D051381:Rats; D013050:Spectrometry, Fluorescence; D015032:Zinc / Q000032:analysis* / Q000737:chemistry
chemical_list: D005029:Ethylenediamines; D007546:Isoquinolines; C531591:N,N,N',N'-tetrakis(1-isoquinolylmethyl)ethylenediamine; D015032:Zinc